If a party bribes voters with their own money, it is illegal. But if they promise to pay/bribe after they will win, that too not from their pocket but country's money, it it legal.
Political parties in India use this huge hole and bribe the voters with TV, loan waivers, unfair reservations for the majority etc... and they do win elections using these cheap means at the cost of the country.
But it is not correct to blame only the politicians, it is the cheap people who are happy, as long as they are benefiting at the cost of ones own country. As long as such cheap, stupid people are majority in a country, the nation is destined to have corrupt politicians.
But the minority who are not really amused by these bribery are at loss. That is the problem with democracy :(
Also I hope one day people would directly vote for policies rather than vote for people who will device policies. But with these kind of people around it would !@$#$%@#%$# I seriously doubt the benefits of democracy. Law should evolve for the society to evolve, but law is becoming extinct.